Impact of abortion incidences on Holstein productivity

Abortion in Holstein cows is a significant reproductive issue, causing substantial financial losses in the dairy industry. This study examined the genetic and phenotypic associations between abortion within the first 150 days of gestation and key productive and reproductive traits in Iranian Holsteins. Data were analyzed using SQL software, with statistical analyses performed via the GLIMMIX procedure in SAS. Variance components and correlations were estimated using a Bayesian approach with Gibbs sampling in DMU software. The average abortion rate was 6.3% (range: 1.6%–14.9%). Factors such as parity, number of inseminations per conception (NI), peak milk yield (PMY), day of peak milk yield (DPY), and somatic cell score (SCS) significantly increased abortion risk (P < 0.01). Cows calving in winter or spring, with higher parity, more NI, or elevated SCS faced greater abortion risks. First-parity cows with higher PMY and multiparous cows with PMY below 40 kg and DPY under 50 days showed elevated abortion rates. Abortion heritability was low (0.08), while peak production traits (milk, fat, protein yield) had moderate heritability (0.17–0.22). Genetic correlations indicated a positive link between abortion, PMY, and SCS, suggesting high milk production adversely affects pregnancy maintenance. Phenotypic correlations between abortion and SCS were positive, highlighting clinical mastitis as a risk factor. Despite low heritability, improved management practices are crucial for reducing abortion risks in Holstein cattle.